1. Field of the Invention
The invention relates to soft switches which can be used with existing household wiring arrangements to effect control from any number of separate stations. The contents of the patents and patent applications referenced in the aforementioned parent case (Ser. No. 768,544) are incorporated herein by reference for the purpose of providing background information.
2. Description of the Prior Art
The concept of soft switching, i.e., gradual "turn-on" and "turn-off", and multiple station control using standard wiring has been disclosed in the parent case and previous patents by the same inventors.
These prior art circuits are, however, complicated. In addition, they do not have the capability of recovering to a previous state if a total power failure occurs. They also suffer from the effects of line voltage changes, particularly with regard to the time delays which occur during turn-on. What is actually desired, therefore, is a simpler and more reliable circuit for achieving soft switching, touch control circuitry whose characteristics are not dependent upon normal line voltage changes, and the state of which is not effected by power failures. In addition, it is desirable to provide an embodiment of the invention which increases the power gradually, thereby extending lamp life, but rapidly enough to provide the appearance of instantaneous "turn-on". It is of further advantage to provide such embodiments with dimming capabilities, whose operation does not effect the turn-on and turn-off characteristics.
Accordingly, a primary object of the invention is to provide a simplified momentary contact light switch which can be used to replace a conventional mechanical toggle switch at any number of control stations.
Another object of the invention is to provide a momentary contact light switch which does not utilize relays or other mechanical devices to retain its state in the event of a power failure.
A further object of the invention is to provide an electronic switch which will reliably respond to the actuation of any number of normally closed series connected mechanical switches.
Another object of the invention is to provide a simplified electronic switch which will eliminate the need for three-way wiring arrangements to effect control of a light from a plurality of separate stations.
Another object of the invention is to provide a zero delay soft switch, which will produce a gradual change in the amount of A.C. power applied to a load immediately following the depression of any one of a plurality of series connected momentary contact switches.
Another object of the invention is to provide gradual "turn-on" and "turn-off" characteristics which are independent of normal line voltage changes.
Another object of the invention is to provide an electronic switch which progressively increases the application of power at a rate which protects lamp filaments, but which provides the appearance of instantaneous or nearly instantaneous "turn-on".
A further object of the invention is to provide an electronic switch and dimmer control which can be turned "on or off" at a remote station.
Another object of the invention is to provide a delayed mechanical shunt across the control element of an electronic switch.
Other objects and advantages of the present invention will be obvious from the detailed description of a preferred embodiment given hereinbelow.